Scaling accurately to relative sizes.

JP
Posted By
Jefferis Peterson
Sep 15, 2004
Views
920
Replies
16
Status
Closed
Hi Folks, I’m updating a jewelery web site for my client and the proprietor is a stickler for accuracy, and since on the web you cannot control display or resolution size, he likes all items scaled relatively so that they reflect the same proportions to one another as they do in life.
This site was originally done before the photographer used digital cameras and now since going digital,the problem for the print production side of the business is that digitial images have no ‘real’ size.
In photoshop, the guy who provides me with the images creates an accurate print size for each item, and I receive the images at 300 dpi, but the pixel dimensions may vary widely between 1000 and 2500 px wide [ depending on the original item’s supposed size, e.g.].
I have used
batch processing in the past to scale images to 35% for thumbnail views and 50% for enlarged views, but I’m running into irregularities. Now, a work flow might be to change image size by scaling in the dialog box for each item, then after it is scaled, reduce the ppi but keep the px dimensions the same. Somehow, things are not uniform.
My question is:
what is the best way to get an accurate scaling down of print accurate phsop created images for the web?
Also, for the web, 96 dpi is
standard for Win and 72 dpi for Macs, how much of a difference in display size will such a dpi difference make when scaling? Jeff


Jefferis Kent Peterson www.PetersonSales.net Flash, Web Design and Marketing

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J
jjs
Sep 15, 2004
"Jefferis Peterson" wrote in message

[… snip good explanation …]
My question is:
what is the best way to get an accurate scaling down of print accurate phsop created images for the web?

Let’s clarify further. Is it the case that objects within the images (for example, rings) are not the same size in each image when displayed or measured as actual pixels?

Also, for the web, 96 dpi is
standard for Win and 72 dpi for Macs, how much of a difference in display size will such a dpi difference make when scaling?

I believe you have some very old information regarding Macs. I’d not worry a bit about the actual, so-called DPI between platforms. Your larger concern, if you care, is gamma differences. It’s a rather losing proposition to try to accomodate the differences to perfection.
W
Wayne
Sep 15, 2004
In article ,
says…

My question is:
what is the best way to get an accurate scaling down of print accurate phsop created images for the web?
Also, for the web, 96 dpi is
standard for Win and 72 dpi for Macs, how much of a difference in display size will such a dpi difference make when scaling?

You cannot get there that way, because dpi has absolutely no meaning on the video screen. Dpi is for printing on paper (paper is dimensioned in inches, but video screens are dimensioned in pixels). Only the pixel dimensions of the image matter on the screen, where it simply does not matter what the image dpi field says. For example, a 1024×768 pixel image will totally fill a 1024×768 pixel screen, regardless if it is 72 dpi or 1072 dpi or any other value. Both the image and the screen are dimesoned in pixels.

On the web page, your goal is surely some image dimension in pixels. Nothing else matters, there is nothing else on the screen.

An easy test of this – If you have two images, both say 400×300 pixels in size, but one at 72 dpi and one at 1072 dpi, both will display on the screen as 400×300 pixels in size (because both are 400×300 pixel images). Only the pixel dimensions matter on the video screen (and web pages are video screens). Dpi in the image file is totally ignored on the video screen in every case, it simply doesnt matter what the dpi says.

Some ifs and buts… Dpi definitly matters to scanners and printers, but not to video. Printers print paper dimensioned in inches, and scanners scan paper dimensioned in inches. Scan 6 inches at 100 dpi, and you create 600 pixels. Or scan 1 inch at 600 dpi, and you create 600 pixels. Or 2 inches at 300 dpi, or 3 inches at 200 dpi etc. But if you have created 600 pixels, regardless of how you did it, then it will display on the video screen as 600 pixels in size, regardless of what the dpi field may indicate. It will fill 600 pixels of the 1024 pixel screen width (or whatever size that screen might be, I assume 1024×768 pixels to have a number), because the image dimension is 600 pixels (and the video screen dimension is 1024 pixels). Digital images are dimensioned in pixels. Video screens are dimensioned in pixels. Video shows pixels, and video simply does not use dpi in any way for images. Scanners and printers do use dpi.

More at site below.

Wayne
http://www.scantips.com "A few scanning tips"
R
RSD99
Sep 15, 2004
Wayne is correct in his description.

This is why most technical photographs, and *all* forensic photography, includes a reference object in the frame. If you are redoing any of the pictures, or making pictures of new items, include a scale or some similar item in the frame …. off to the side would be OK … so that the actual size can be determined later. For jewelry, such as a ring, why not use something like a ring-stand that has a known
dimension?

"Wayne Fulton" wrote in message
In article ,
says…

My question is:
what is the best way to get an accurate scaling down of
print accurate
phsop created images for the web?
Also, for the web, 96 dpi is
standard for Win and 72 dpi for Macs, how much of a
difference in
display size will such a dpi difference make when
scaling?
You cannot get there that way, because dpi has absolutely
no meaning on
the video screen. Dpi is for printing on paper (paper is
dimensioned in
inches, but video screens are dimensioned in pixels).
Only the pixel
dimensions of the image matter on the screen, where it
simply does
not matter what the image dpi field says. For example, a
1024×768 pixel
image will totally fill a 1024×768 pixel screen,
regardless if it is 72
dpi or 1072 dpi or any other value. Both the image and the
screen are
dimesoned in pixels.

On the web page, your goal is surely some image dimension
in pixels.
Nothing else matters, there is nothing else on the screen.
An easy test of this – If you have two images, both say
400×300 pixels in
size, but one at 72 dpi and one at 1072 dpi, both will
display on the
screen as 400×300 pixels in size (because both are 400×300
pixel images).
Only the pixel dimensions matter on the video screen (and
web pages are
video screens). Dpi in the image file is totally ignored
on the video
screen in every case, it simply doesnt matter what the dpi
says.
Some ifs and buts… Dpi definitly matters to scanners
and printers, but
not to video. Printers print paper dimensioned in inches,
and scanners
scan paper dimensioned in inches. Scan 6 inches at 100
dpi, and you
create 600 pixels. Or scan 1 inch at 600 dpi, and you
create 600 pixels.
Or 2 inches at 300 dpi, or 3 inches at 200 dpi etc. But
if you have
created 600 pixels, regardless of how you did it, then it
will display on
the video screen as 600 pixels in size, regardless of what
the dpi field
may indicate. It will fill 600 pixels of the 1024 pixel
screen width (or
whatever size that screen might be, I assume 1024×768
pixels to have a
number), because the image dimension is 600 pixels (and
the video screen
dimension is 1024 pixels). Digital images are dimensioned
in pixels.
Video screens are dimensioned in pixels. Video shows
pixels, and video
simply does not use dpi in any way for images. Scanners
and printers do
use dpi.

More at site below.

Wayne
http://www.scantips.com "A few scanning tips"
JP
Jefferis Peterson
Sep 15, 2004
In jjs wrote:
[… snip good explanation …]
My question is:
what is the best way to get an accurate scaling down of print accurate phsop created images for the web?

Let’s clarify further. Is it the case that objects within the images ( for example, rings) are not the same size in each image when displayed or measured as actual pixels?

Thanks Wayne and John.

Wayne’s explanation tells me why what I did isn’t working 🙂

Here’s what I need to do for the client, by way of clarification.

The print house modify the images they receive from the digitial photographer for print in brochures. They make sure that the print size of the images is exactly the real size of the image in inches. Now I have all the images in photoshop with the actual physical print size dimensions, but the pixel dimensions of each photo will vary widely. They all are, for the most part, are in 300 dpi for print output.

What I need to do is scale the images on screen so that they are relatively the same size to one another, so that a diamond ring looks proportionally smaller than an enamel brooch or necklace, e.g. Since the only exact measurement I have is the print size, how do I assure that any scaling I do will reflect the appearance? If, as Wayne is saying, I may be screwed because I may get images with various screen pixel dimensions that have nothing to do with their physical sizes…

But assuming this can work, is there a way to standardize the original images to lock pixel dimensions to print size???

Jeff

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JP
Jefferis Peterson
Sep 15, 2004
In Jefferis Peterson
wrote:
In jjs wrote:

Oops! My bad, I was thinking of print output, but the images in Pshop are actually 300 ppi, not dpi.
So, am I saved? Is there a proper method for scaling this images which have uniform ppi and whose print sizes are actual size? I think I made a mistake reducing the ppi to 72 ppi before scaling…

Jeff

Thanks Wayne and John.

Wayne’s explanation tells me why what I did isn’t working 🙂
Here’s what I need to do for the client, by way of clarification.
The print house modify the images they receive from the digitial photographer for print in brochures. They make sure that the print size of the images is exactly the real size of the image in inches. Now I have all the images in photoshop with the actual physical print size dimensions, but the pixel dimensions of each photo will vary widely. They all are, for the most part, are in 300 dpi for print output.

What I need to do is scale the images on screen so that they are relatively the same size to one another, so that a diamond ring looks proportionally smaller than an enamel brooch or necklace, e.g. Since the only exact measurement I have is the print size, how do I assure that any scaling I do will reflect the appearance? If, as Wayne is saying, I may be screwed because I may get images with various screen pixel dimensions that have nothing to do with their physical sizes…
But assuming this can work, is there a way to standardize the original images to lock pixel dimensions to print size???

Jeff

—–= Posted via Newsfeeds.Com, Uncensored Usenet News =—– http://www.newsfeeds.com – The #1 Newsgroup Service in the World! —–== Over 100,000 Newsgroups – 19 Different Servers! =—–

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in article , Jefferis Peterson
at wrote on 09/15/2004 11:49 AM:

Thanks John & Wayne for http://www.artistmike.com .

Not a problem "pilgrim".
in article , Jefferis Peterson
at wrote on 09/15/2004 11:56 AM:

Oops! My bad, I was thinking of http://www.artistmike.com and could not concentrate on your question.

It happens.
T
Theo
Sep 15, 2004
"RSD99" wrote in news:1N_1d.6181$:

This is why most technical photographs, and *all* forensic photography, includes a reference object in the frame. If you are redoing any of the pictures, or making pictures of new items, include a scale or some similar item in the frame … off to the side would be OK … so that the actual size can be determined later. For jewelry, such as a ring, why not use something like a ring-stand that has a known
dimension?

Also bear in mind that the default in IE will scale an image down to fit inside a window if its too big.
in article , Theo at
wrote on 09/15/2004 12:16 PM:

"RSD99" wrote in news:1N_1d.6181$:

This is why most technical photographs, and *all* forensic photography, includes a reference object in the frame. If you are redoing any of the pictures, or making pictures of new items, include a scale or some similar item in the frame … off to the side would be OK … so that the actual size can be determined later. For jewelry, such as a ring, why not use something like a ring-stand that has a known
dimension?

Also bear in mind that http://www.artistmike.com is the best site on the web.

I know.
W
Wayne
Sep 15, 2004
In article ,
says…

The print house modify the images they receive from the digitial photographer for print in brochures. They make sure that the print size of the images is exactly the real size of the image in inches. Now I have all the images in photoshop with the actual physical print size dimensions, but the pixel dimensions of each photo will vary widely. They all are, for the most part, are in 300 dpi for print output.
What I need to do is scale the images on screen so that they are relatively the same size to one another, so that a diamond ring looks proportionally smaller than an enamel brooch or necklace, e.g. Since the only exact measurement I have is the print size, how do I assure that any scaling I do will reflect the appearance? If, as Wayne is saying, I may be screwed because I may get images with various screen pixel dimensions that have nothing to do with their physical sizes…
But assuming this can work, is there a way to standardize the original images to lock pixel dimensions to print size???

If every one of your images already print at the correct size on paper at 300 dpi as is, then you can simply scale them all proportionally, like each one to 25% size in pixel dimensions, which will maintain that size ratio between their video sizes too, and about 25% or 33% is probably near your size goal.

However, if when printing accurate size, if to do that, if some print at 220 dpi, some at 300 dpi, and some at 320 dpi to do that, then that changes things. The same 25% wont do it.

How it works: If you have an image with say 1200 pixels in one dimension, and if you print that image at 300 dpi (pixels per inch on paper), then it will be 1200 pixels / 300 dpi = 4 inches printed size on paper in that dimension. pixels per inch. This is the definition of terms.

But if you print those same 1200 pixels at say 220 dpi, then it will print 1200 pixels / 220 dpi = 5.4 inches on paper. Specifically 300/220 = 1.36x larger on paper (that ratio of pixels per inch spacing on paper). This
5.4 inches probably is the correct intended accurate printed size for that
one image that was marked 220 dpi (the goal and purpose of the 220 dpi is to establish this printed size on paper.. pixels per inch), but when scaling them all, you will have to take these differences into account, if they are not all the same dpi for printing.

So if these images vary in this way (dpi for printed size varies), but are otherwise all the accurate printed size on paper (if you really can trust that is true, and it wasnt resized again before printing), then instead of resamplng to 25% size, you can instead resample them all to say 75 or 100 dpi "size" in the Photoshop resample box. This technically would imply you are planning to print them the same size (inches) on paper, but to be 75 or 100 dpi quality on paper. Note that this is NOT resampling to 75 dpi for the screen, because the video screen doesnt know, doesnt care about any dpi number, only pixels. But, if this 75 or 100 dpi size is the only reampling change, the size in inches they would print on paper is not changed (you can check that, keep an eye on it to make sure), but only the quality changes when printed (and of course the image size in pixels is smaller). But we dont plan to print them, and quality is not the issue. Video size is the issue. The new image dimensions in pixels will change in accordance to their original printed size ratio and the new 75 dpi size, by the ratio of those numbers. Printed quality is not the plan here of course, but it incidentally also has the effect of intermediately resampling them all to the same printed size ratio, but of much smaller dimensions in pixels, which will be more appropriate for the screen (which is the goal here). The video screen couldnt care less what the dpi says, but it does care about image size in pixels. So the number 75 or 79 or 100 or 124 dpi is totally unimportant, pick the one that gives the image size you want to use on the screen. But about 100 dpi may be about right.

Repeating for clarity, if all do print accurate size on paper, then simply resample all to say 75 dpi size. If that is too small for your video goal, then discard and start over from the originals, and try 100 dpi for a little larger. But do them all the same, and if they did print original size, they will still maintain approximate size relationship on the screen too. If they originally printed accurate size on paper, then 75 to 100 dpi size will be somewhere closer to ball park actual size on the screen in many cases.

It is surely confusing, because the only significance of 75 or 100 dpi scan size is that the scanned object is somewhat near approximate actual size on many commonly used video screen sizes, so you can use that here (as a size). However, it doesnt mean the video cares at all about dpi, and it does not mean that exact actual size is possible on the screen. So I am NOT saying resample to 75 dpi because the video cares one way or the other. Video screens vary in size, but 75 to 100 dpi size can be approximately rough ballpark actual size in crudest terms, which is all that is possible on multiple screens, because screens vary in size. I am just saying 75 or 100 dpi is likely a suitable ratio between accurate printed size on paper (whatever it is) and smaller appropriate size for a video image.


Wayne
http://www.scantips.com "A few scanning tips"
W
Wayne
Sep 15, 2004
In article ,
says…

Oops! My bad, I was thinking of print output, but the images in Pshop are actually 300 ppi, not dpi.
So, am I saved? Is there a proper method for scaling this images which have uniform ppi and whose print sizes are actual size? I think I made a mistake reducing the ppi to 72 ppi before scaling…

Same thing, it doesnt matter dpi or ppi. ppi and dpi are simply two names for exactly the same thing, exactly the same meaning if related to images and printing resolution. Both terms mean "pixels per inch" and there is no difference at all. This confuses some of the newbies who think this surely must be "wrong" somehow, but dpi is simply what it has historically always been called, for many years longer than we had printers that could print images. However, printer head positioning ratings (ink drop ratings) are indeed something different, a different meaning, but that is not the subject here. The term means the only thing it can mean in the context it is used (like all other English words <g>)


Wayne
http://www.scantips.com "A few scanning tips"
R
RSD99
Sep 16, 2004
CORRECTION

RSD99 **never** posted the phrase

"Also bear in mind that http://www
(dot) artistmike
(dot) com
is the best site on the web."

This posting was fraudulently Hijacked by some idiot calling himself … well you know what *he* actually is …

Now … LittleMikie … your "bag of tricks" is really very limited. You really are beginning to bore us. Why don’t you just admit that things are tough, your money’s getting low, the bill-collectors are banging on your door, and you really **NEED** a bunch of "hits" on your web site to generate some sorely-needed cash.
R
RSD99
Sep 16, 2004
Good point … which probably actually makes it impossible to do what the OP is trying to do!

"Theo" wrote in message
"RSD99" wrote in
news:1N_1d.6181$:
This is why most technical photographs, and *all*
forensic
photography, includes a reference object in the frame.
If
you are redoing any of the pictures, or making pictures
of
new items, include a scale or some similar item in the
frame
… off to the side would be OK … so that the actual
size
can be determined later. For jewelry, such as a ring,
why
not use something like a ring-stand that has a known
dimension?

Also bear in mind that the default in IE will scale an
image down to fit
inside a window if its too big.
in article UZ72d.10652$
wrote on 09/15/2004 8:43 PM:

You really are beginning to bore us.

Got one reason why anyone should care about your state of boredom?
BO
BIG ONE
Sep 16, 2004
On Wed, 15 Sep 2004 21:05:27 -0700, Danhiel – SoupOrNews Admin wrote:

in article UZ72d.10652$
wrote on 09/15/2004 8:43 PM:

You really are beginning to bore us.

Got one reason why anyone should go to http://www.artistmike.com ?

erm … i can think of more reasons 2 use the plonk … but i won’t
in article , BIG ONE at
wrote on 09/15/2004 10:27 PM:

erm … i can think of more reasons 2 use the plonk … but i won’t

Do it now mister!

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